茂兰喀斯特森林小生境类型对土壤微生物群落组成的影响

喀斯特山区是我国典型的生态脆弱区,区内分布复杂多样的小生境类型(石洞、石缝、石沟、石槽、土面等)。土壤微生物是陆地生态系统最活跃的成分,推动着生态系统能量流动和物质循环。研究不同小生境类型对土壤微生物群落组成的影响,对于喀斯特山区森林土壤微生物特征的认识和生态保护具有积极的意义。以贵州茂兰喀斯特森林小生境为对象,对其土壤理化性质和微生物组成进行了比较分析,并对小生境类型进行了数量聚类。结果表明:6种小生境土壤中共检测到48种磷脂脂肪酸(PLFA),其中,标记土壤微生物的特征PLFA有18种;土壤微生物总量、细菌、真菌、放线菌、G~+、G~-的含量均表现为石槽石沟土面表层石洞石缝土面下层,同时,各微生物类型的含量在不同生境类型中表现为细菌放线菌真菌; G~+/G~-在六种生境中表现为石槽石沟土面表层石缝石洞土面下层;真菌/细菌变幅为0.14—0.16,具体表现为土面表层石缝石沟石槽石洞土面下层;相关性分析和多元回归树分析显示,不同小生境类型的土壤有机质是影响土壤微生物群落组成的首要因子。聚类结果表明,小生境可划分为石槽-石沟型、石洞-石缝型、土面表层型以及土面下层型4种生境类型。研究结果证实了不同小生境类型对微生物分布特征存在显著影响。

Effects of different microhabitat types on soil microbial community composition in the Maolan Karst Forest in Southwest China

Karst mountain areas are typically known as ecologically fragile areas in China. There are a variety of microhabitats that are distributed over the area, including stone grooves, stone gullies, top-soils, stone caverns, and stone crevices. Soil microorganisms are the most active components of terrestrial ecosystems, and they promote energy flow and material circulation through the ecosystem. Studies that examine the impact of different types of microhabitats on the composition of soil microbial communities have great significance for the better understanding of the microbial characteristics of karst forest in mountain area and the karst ecological protection. With the Maolan Karst Forest microhabitats as the research subjects, this study comparatively analyzed soil physical and chemical properties and microbial composition, and it quantitatively clustered the microhabitats. The results showed that 48 phospholipid fatty acids (PLFAs) were detected in the soils of six microhabitat types, and among these, there were 18 unique PLFAs that characterized microbes. The contents of total microbes, bacteria, fungi and actinomycetes, G⁺, and G^- in all microhabitat types were in the following order:stone groove > stone gully > top-soil > stone cavern > stone crevice > sub-soil. Moreover, the microbial contents in all habitats were in the following order:bacteria > actinomycetes > fungi. The values of G⁺/G^- in all habitats were as follows:stone groove > stone gully > top-soil > stone crevice > stone cavern > sub-soil. The ratios of fungi/bacteria ranged from 0.14 to 0.16, and the ratios were ordered as follows:top-soil > stone crevice > stone gully > stone groove > stone cavern > sub-soil. Correlation and Multivariate Regression Tree (MRT) analyses showed that soil organic matter from a different microhabitat was the primary factor affecting soil microbial community composition. The results of MRT clustering showed that the karst forest microhabitat can be divided into four types:stone groove-stone gully type, stone cavern-stone crevice type, top-soil type, and sub-soil type. The results confirmed that microhabitat types had significant impacts on soil microbe distribution in the karst forest.